Command-line interface
The bezierkit command, installed with the cli extra, evaluates, samples
and constructs curves from the shell. Its output is a table by default, or
JSON or CSV for other programs.
bezierkit evaluate --points "0,0" --points "1,2" --points "3,2" --points "4,0" \
--t 0.5 --order 1 --json
# [{"t":0.5,"value":[4.5,0.0]}]
Control points
Commands that take a curve accept its control points as repeated --points
options, each a comma-separated list of coordinates ("1,2", or "1,2,3" in
three dimensions). Without --points, they read a JSON object with a
control_points array from standard input, which is what construct
writes, so commands can be piped together.
Commands
bezierkit evaluate --t values [--points ...] [--order int] [--json]Evaluate the curve, or its derivative of order --order (default 0), at
each --t. A value is a number or an inclusive range start:stop:step,
such as 0:1:0.25; --t may be repeated.
bezierkit sample [--points ...] [--count int] [--format table|csv|json] [--output path]Sample the curve at --count (default 50) equally spaced parameters,
ends included, as rows of t, x, y (and z, or c3, c4, ... in
higher dimensions). --output writes to a file instead of standard
output.
bezierkit construct slopes --start point --end point --start-slope float --end-slope float [--start-handle --end-handle]
bezierkit construct tangents --start ... --end ... --start-direction vector --end-direction vector [...]Build a cubic with PlanarSlopes or TangentDirections
(Constructions and Hermite interpolation) and print its control points as JSON.
bezierkit construct slopes --start "0,5" --end "5,0" \
--start-slope -2 --end-slope -0.3 \
| bezierkit sample --count 3 --format csv
# t,x,y
# 0.0,0.0,5.0
# 0.5,2.3085202413545525,2.272345260462411
# 1.0,5.0,0.0
Errors
Invalid input, such as a malformed point or a parameter outside \([0, 1]\), is
reported on standard error as Error: ... with exit status 1 and no
traceback. Put the global option --debug before the command to see the
Python traceback instead.